gcc/ada/1ssecsta.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --               S Y S T E M . S E C O N D A R Y _ S T A C K                --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2001 Free Software Foundation, Inc.          --
  10 --                                                                          --
  11 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  12 -- terms of the  GNU General Public License as published  by the Free Soft- --
  13 -- ware  Foundation;  either version 2,  or (at your option) any later ver- --
  14 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  15 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  16 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  17 -- for  more details.  You should have  received  a copy of the GNU General --
  18 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  19 -- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
  20 -- MA 02111-1307, USA.                                                      --
  21 --                                                                          --
  22 -- As a special exception,  if other files  instantiate  generics from this --
  23 -- unit, or you link  this unit with other files  to produce an executable, --
  24 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  25 -- covered  by the  GNU  General  Public  License.  This exception does not --
  26 -- however invalidate  any other reasons why  the executable file  might be --
  27 -- covered by the  GNU Public License.                                      --
  28 --                                                                          --
  29 -- GNAT was originally developed  by the GNAT team at  New York University. --
  30 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  31 --                                                                          --
  32 ------------------------------------------------------------------------------
  33
  34 --  This is the HI-E version of this package.
  35
  36 with Unchecked_Conversion;
  37
  38 package body System.Secondary_Stack is
  39
  40    use type SSE.Storage_Offset;
  41
  42    type Memory is array (Mark_Id range <>) of SSE.Storage_Element;
  43
  44    type Stack_Id is record
  45       Top  : Mark_Id;
  46       Last : Mark_Id;
  47       Mem  : Memory (1 .. Mark_Id'Last);
  48    end record;
  49    pragma Suppress_Initialization (Stack_Id);
  50
  51    type Stack_Ptr is access Stack_Id;
  52
  53    function From_Addr is new Unchecked_Conversion (Address, Stack_Ptr);
  54
  55    function Get_Sec_Stack return Stack_Ptr;
  56    pragma Import (C, Get_Sec_Stack, "__gnat_get_secondary_stack");
  57    --  Return the address of the secondary stack.
  58    --  In a multi-threaded environment, Sec_Stack should be a thread-local
  59    --  variable.
  60
  61    --  Possible implementation of Get_Sec_Stack in a single-threaded
  62    --  environment:
  63    --
  64    --     Chunk : aliased Memory (1 .. Default_Secondary_Stack_Size);
  65    --     for Chunk'Alignment use Standard'Maximum_Alignment;
  66    --     --  The secondary stack.
  67    --
  68    --     function Get_Sec_Stack return Stack_Ptr is
  69    --     begin
  70    --        return From_Addr (Chunk'Address);
  71    --     end Get_Sec_Stack;
  72    --
  73    --  begin
  74    --     SS_Init (Chunk'Address, Default_Secondary_Stack_Size);
  75    --  end System.Secondary_Stack;
  76
  77    -----------------
  78    -- SS_Allocate --
  79    -----------------
  80
  81    procedure SS_Allocate
  82      (Address      : out System.Address;
  83       Storage_Size : SSE.Storage_Count)
  84    is
  85       Max_Align    : constant Mark_Id := Mark_Id (Standard'Maximum_Alignment);
  86       Max_Size     : constant Mark_Id :=
  87                        ((Mark_Id (Storage_Size) + Max_Align - 1) / Max_Align)
  88                          * Max_Align;
  89       Sec_Stack    : constant Stack_Ptr := Get_Sec_Stack;
  90
  91    begin
  92       if Sec_Stack.Top + Max_Size > Sec_Stack.Last then
  93          raise Storage_Error;
  94       end if;
  95
  96       Address := Sec_Stack.Mem (Sec_Stack.Top)'Address;
  97       Sec_Stack.Top := Sec_Stack.Top + Mark_Id (Max_Size);
  98    end SS_Allocate;
  99
 100    -------------
 101    -- SS_Free --
 102    -------------
 103
 104    procedure SS_Free (Stk : in out System.Address) is
 105    begin
 106       Stk := Null_Address;
 107    end SS_Free;
 108
 109    -------------
 110    -- SS_Init --
 111    -------------
 112
 113    procedure SS_Init
 114      (Stk  : System.Address;
 115       Size : Natural := Default_Secondary_Stack_Size)
 116    is
 117       Stack : Stack_Ptr := From_Addr (Stk);
 118    begin
 119       pragma Assert (Size >= 2 * Mark_Id'Max_Size_In_Storage_Elements);
 120
 121       Stack.Top := Stack.Mem'First;
 122       Stack.Last := Mark_Id (Size) - 2 * Mark_Id'Max_Size_In_Storage_Elements;
 123    end SS_Init;
 124
 125    -------------
 126    -- SS_Mark --
 127    -------------
 128
 129    function SS_Mark return Mark_Id is
 130    begin
 131       return Get_Sec_Stack.Top;
 132    end SS_Mark;
 133
 134    ----------------
 135    -- SS_Release --
 136    ----------------
 137
 138    procedure SS_Release (M : Mark_Id) is
 139    begin
 140       Get_Sec_Stack.Top := M;
 141    end SS_Release;
 142
 143 end System.Secondary_Stack;